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Microbiology > Lectures 4-6 > Flashcards

Lectures 4-6 Flashcards

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Biology 101 flashcards
1
Q

antibiotics

A

naturally occurring antimicrobial drugs

used in the treatment and prevention of bacterial infections
may either kill or inhibit the growth of bacteria

e.g. streptomycin

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2
Q

aminoglycoside

A

antibiotics containing amino sugars
contain glycosidic bonds
eg. kanamycin

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3
Q

semi-synthetic antibiotic

A

modified naturally occurring antibiotic

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4
Q

macrolides

A

contain lactone rings

e.g. erythromycin
Broad-spectrum antibiotic
targets the 50S subunit of ribosome

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5
Q

tetracycline

A

contains 4 rings

widespread medical use in humans and animalsBroad-spectrum inhibition of protein synthesis
Inhibits functioning of 30S ribosomal subunit

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6
Q

quinolones

A

synthetic anitibiotic

causes inhibition of DNA gyrase by binding to the A subunit of DNA gyrase

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7
Q

most important group of antibiotics

A

beta-lactam

includes: penicillins, cephalosporins, and cephamycins

Over half of all antibiotics used worldwide are beta-lactam

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8
Q

penicillin

A

Alexander Fleming
Primarily effective against Gram-positive bacteria

Some synthetic forms are effective against some Gram-negative bacteria
Target cell wall synthesis

bacteriolytic effect on bacterial growth

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9
Q

3 effects of antibiotics on bacterial growth

A

bacteriolytic - inhibit cell wall synthesis e.g. penicillin

bacteriocidal - kill bacteria

bacteriostatic - slow bacterial growth/reproduction

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10
Q

how do you measure antibacterial activity

A

liquid culture poured onto agar plate

discs containing antimicrobial agents placed onto agar

incubated 24-48hrs

culture will show susceptibility to agents if bacterial growth inhibition seen around discs

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11
Q

why might antibiotics cause adverse side effects

A

they act on similar eukaryotic structures and processes

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12
Q

vancomycin

A

inhibits cell wall biosynthesis

however poor bioavailability

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13
Q

minimising resistance

A

only use antibiotics when needed and correctly

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14
Q

how may antibiotic resistance form

A

Organism lacks structure the antibiotic inhibits
Organism is impermeable to antibiotic
Organism can inactivate the antibiotic
Organism may modify the target of the antibiotic
Organism may be able to pump out the antibiotic (efflux)

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15
Q

examples of essential processes that antibiotics target

A

central dogma - transcription/translation

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16
Q

folic acid

A

precursor for DNA

bacteria can’t make their own - need to obtain it
they interfere with folic acid synthesis and prevent DNA forming

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17
Q

EFB

A

endospore forming bacteria

e.g. bacillus

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18
Q

taxonomy

A

the science of classification

  • identifies relationships between groups of organisms
  • universal
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19
Q

taxa

A

categories of organism

  • relatedness is a result of evolutionary history or phylogeny
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20
Q

prokaryotes

A

no membrane bound nucleus or organelles

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21
Q

gram positive bacteria

A

thick peptidoglycan layer

positive stain test - stains crystal violet

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22
Q

gram negative bacteria

A

do not retain violet stain due to thin peptidoglycan layer
counter stained with safranin
sugar chains off outer membrane

23
Q

further divisions of gram +ve bacteria

A

Firmicutes - Low G+C (<30% GC)

Actinobacteria - High G+C (60/70% GC)

24
Q

firmicutes

A

low g+c gram +ve bacteria

e.g.
lactobacilalles
- lactobacillus (used in fermented products e.g. yoghurt)
- streptococcus (medically relevant)
bacilalles
- staphylococcus (boils)
- bacillus (rod-shaped, endospore forming)
clostridiales
- clostridium (rod-shaped, form endospores,medically important)

tolerant to low pH
acid by-products e.g. lactic acid, butyric acid, acetic acid

25
Q

actinobacteria

A

high g+c gram +ve bacteria

actinomycetales

  • Actinomyces
    (filamentous, some human pathogens, facultative anaerobe, soil ecology)
  • Frankia
    (symbiotic nitrogen fixers)
  • Streptomyces
    (filamentous, produce antibodies and spores called
    e.g. aminoglycosides, tetracyclines)

similar appearance to fungi

26
Q

proteobacteria

A

gram -ve

  • metabolically diverse
  • many environmental habitats e.g. soil, aquatics
  • many are nitrogen fixing
27
Q

examples of proteobacteria

A

Alpha - α
- Bradyrhizobium/Rhizobium
(Form symbiosis with plants and fix nitrogen to ammonia)

Beta - β
- Neisseria
(Characteristic diplococci, medically important, meningitis)

Gamma - γ
- Shigella/ Salmonella
(Responsible for serious food poisoning)
- Escherichia
(Common inhabitant of intestinal tract but uncommon pathogen (O157:H7)
Very important research tool e.g. E. coli)

Delta - δ
- Campylobacter
(Highly motile bacillus, curved
Medically important species, foodborne disease – C. jejuni)
- Helicobacter
(Has multiple flagella
Cause of stomach ulcers - H. pylori)

Epsilon - ε

28
Q

why do we know so much about bacteria

A

easy to culture and grow in a lab

29
Q

Gamma/γ proteobacteria

A

most common subdivision

contains most pathogens

30
Q

how can you study non-culturable bacteria

A

Fluorescent oligonucleotides that bind specific DNA

31
Q

FISH

A

fluorescent in situ hybridisation

different coloured oligonucleotides match different 16S rRNA sequences

can identify complexity of bacterial group

32
Q

ecosystem

A

sum of all organisms and abiotic factors in an environment

contains many different habitats

33
Q

abiotic

A

non-living physical and chemical

34
Q

symbiosis

A

mutualism - both species benefit

commensalism - one species benefits, one not affected

35
Q

syntrophy

A

Two or more organisms catabolising a nutrient that can not be catabolised by one on its own

36
Q

species richness

A

total number of species in an ecosystem

37
Q

species abundance

A

the proportion of each species in an ecosystem

38
Q

why do bacteria grow more quickly in a lab

A

no limited resources of nutrients
nutrients are localised and not widely distributed
they dont have to grow in mixed populations

39
Q

photic zone

A

200m below surface

archaea more suited to environment below photic zone

40
Q

pelagic zone

A

nutrient poor

41
Q

root nodule bacteria symbiosis with legumes

A

rhizobia (gram -ve)

ammonia created from atmospheric nitrogen
ammonia used by plant to make amino acids and nucleotides
plant provides bacteria with sugars

42
Q

role of gut microbiome in obesity

A

more methanogens means low H2 and more fermentation (CH4 produced) - more obesity

43
Q

pH in the gut

A

low pH2 in stomach

increases to pH7 by colon

44
Q

baltmore method

A

method of classification of viruses

based on mode of replication and genome type

45
Q

5 virus taxonomic groups

A 
order (-virales)
family (-viridae)
subfamily (-virinae)
genus (-virus)
species
46
Q

viruses

A

non-living entities

extracellularly exist as virions

utilise host proteins upon infection for their propagation

47
Q

nucleocapsid

A

nucleic acid

surrounded by a capsid (membrane made up of capsomers)

48
Q

virophage

A

virus that infects the mimivirus - recently discovered

49
Q

bacteriophage

A

virus of bacteria

50
Q

lifestyle of bacteriophage

A
  1. virion attaches to host bacteria
  2. viral DNA penetrates and enters host, protein coat remains outside
  3. synthesis of nucleic acid and protein
  4. assmebly and packaging
  5. release/lysis of newly formed virions
51
Q

temperate bacteriophage lifestyle

A

lytic pathway

  • viral DNA replicates
  • protein coats are synthesized
  • viral particles burst out of cell during lysis
  • occurs if cro gene dominates

lysogenic pathway

  • viral genome (prophage) enters into host chromosone
  • viral DNA replicated with host DNA
  • occurs if cl gene dominates
52
Q

lytic pathway stages

A
  1. transcription and translation of N and cro from the P
  2. longer transcripts are made with help of N protein (N binds RNA polymerase to read termination sequences allowing further transcription)
  3. stimulation of phage structural gene synthesis by Q protein
53
Q

lysogenic pathway stages

A
  1. lambda repressor protein (cl) synthesis from P
  2. cl and cro compete for transcription
  3. lambda repressor protein (cl) blocks synthesis from lytic pathway genes
  4. lysogenic pathway begins when cl is transcribed and translated

Microbiology (6 decks)

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